2004: Toward a Generalized Friction Controller: From the Bowed String to Unusual Musical Instruments

Abstract

We present case studies of unusual instruments that share the same excitation mechanism as that of the bowed string. The musical saw, Tibetan singing bow, glass harmonica, and bowed cymbal all produce sound by rubbing a hard object on the surface of the instrument. For each, we discuss the design of its physical model and present a means for expressively controlling it. Finally, we propose a new kind of generalized friction controller to be used in all these examples.

Appendices

Author Commentary: About Generalized Friction Controllers

Stefania Serafin and Diana Young

This paper, exploring the concept of a generalized friction controller, reflects the work performed as part of our Ph.D. dissertations. Stefania’s dissertation, defended at the Centre for Computer Research in Music at Acoustics (CCRMA) at Stanford University in 2003 was entitled: “The Sound of Friction: Real-time models, playability and musical applications.” In this dissertation several real-time friction models for sound synthesis were presented, with applications to simulating bowed string instruments and also glass harmonicas, tibetan singing bowls, musical saws and other unusual friction-driven musical instruments. Diana’s dissertation, completed in 2007 at Massachusetts Institute of Technology, was entitled: “A Methodology for Investigation of Bowed String Performance Through Measurement of Violin Bowing Technique.” As part of this work, Diana built the Hyperbow, a high-precision wireless sensing system, to measure violin bowing parameters.

The topics of our dissertations overlapped nicely, and when we met in 2002 at the CCRMA summer workshop on Physical Interaction Design for Music, we decided to collaborate. An obvious collaboration was to use Diana’s Hyperbow controller to drive Stefania’s bowed string physical models. The use of physical models in new interfaces for musical expression supports a natural interaction between performer and resulting sound, as the performer is given control of the physical parameters of the model in a manner that resembles the control of the real instrument counterpart. This is clear for the case of the Hyperbow, which is an augmented bow controller that naturally lends itself to the control of bowed string physical models, enabling any bowed string player to access to the expressive possibilities of virtual string instruments. This work has been published in several venues, such as the 2003 Symposium of Musical Acoustics (Serafin and Young 2003), the 2003 edition of the New Interfaces for Musical Expression Conference (Young and Serafin 2003), and the proceedings of the 2007 International Computer Music Conference (Young and Serafin 2007). In addition to this body of work, the Hyperbow, once adapted for use with acoustic and electric cello, served as an integral part of a collaboration with composers and cellists at the Royal Academy of Music, the focus of which was to further explore its expressive musical potential (Young et al. 2006).

The paper is mostly an overview of digital friction-driven musical instruments and their potential for natural control in expressive performances. In particular, we proposed several realistic gesture controllers to drive models of friction-driven instruments, such as tibetan singing bowls, musical saws and bowed cymbals. For controlling the Glass Harmonica and Tibetan singing bowl we suggest to use the HyperPuja (Young and Essl 2003), a wireless controller in the form of a stick with embedded sensors hidden inside. For controlling the musical saw and bowed cymbals, we proposed the use of an augmented bow controller.

Writing this commentary, we realized it has been more than ten years since our collaboration, so it also gave us the opportunity to review recent work in the bowed string research community. While research on bowed string synthesis and control has continued to grow steadily, there has not been much significant progress in the development of realistic controllers for these virtual instruments that preserve traditional playing techniques. As bowed string enthusiasts, we still believe in the tremendous potential of this paradigm for musical expression. However, creating a faithful match between controller and model, e.g., of a violin, is challenging, especially given the high expectations for the traditional acoustic counterparts.

Given the advances in sensor technology and wireless communication that have occurred since our last contributions, which pre-dated the smart phone revolution, we believe the time is right for serious re-investigation into controllers for bowed string physical models. In addition to the improved affordability and miniaturization of electronics, materials and access to fabrication tools have also increased. In the case of bowed strings, we believe it is now possible to dramatically improve upon the sensing system of the Hyperbow by making it more precise, while also streamlining its ergonomics by embedding it within the construct of a traditional carbon fiber bow. Similarly, the model could be made to run locally within the body of the violin controller, rather than relying on an external computer. Such advances would further support the relationship between the player and instrument, and the development of a new repertoire for virtual strings.

Expert Commentary: Some Thoughts on Friction and Physicality Within Past and for Future NIME Research

Lauren Hayes

Stefania Serafin and Diana Young present a paper which identifies friction as the force that is employed within the excitation mechanism of four unique types of acoustic instrument. They recognise that each instrument sounds as the result of a hard object being rubbed on part of the instrument’s surface. Rather than focussing on the commonly modelled bowed string, they pick four instruments with a diverse sonic palette: the musical saw, Tibetan singing bow, glass harmonica, and bowed cymbal. The Tibetan singing bowl, for example, needs to be activated by a suede-clad stick that is moved in circles around its inner rim.

The authors consolidate a significant body of research within this short paper by describing their designs of both the physical models of these instruments, as well as devices that can be used to play them. For example, Serafin’s contribution to banded waveguide synthesis techniques (Essl et al. 2004) is employed to establish a physical model of a Tibetan bowl. Each prominent resonance within the bowl’s ringing sound is represented by a waveguide, and various beating effects can be achieved by subsequently detuning these. Similarly, Young’s Hyperbow interface, which she has developed and revised extensively over many years, is used to play models of a musical saw and bowed cymbal.

The crux of Serafin and Young’s short paper lies in the authors’ abilities to observe commonalities between the playing mechanisms of these unique instruments. They ask whether a new type of interface might offer a performer playing physical models of the acoustic versions further possibilities for exploration. They propose a generalised friction controller which would allow for combinations of gestures such as circular movements (stick), as well as back-and-forth motions (bow). This goal is realised in later work (Gelineck and Serafin 2010), in which a two-dimensional friction device is built and included as part of a larger instrument, PHYSMISM, which is designed to play and combine physical models.

The authors emphasise physicality as a key consideration for the design of NIMEs. They suggest that performer–instrument interaction needs to be “natural and instinctive,” and they talk about achieving “easy intuitive control.” The notion of control is problematic when discussing musical instruments. As I have written previously, hybrid pianos, just as acoustic pianos, are played rather than controlled (Hayes 2013). When performing with systems that are, for example, unpredictable in part, it may be precisely the lack of control that allows us to fully engage with the instrument. Creative possibilities may be thrown our way, as we attempt to navigate through a performance. Similarly, it is important to carefully consider whether new instruments should be easy to play when developing a design philosophy.

Serafin and Young clearly recognise the importance of the relationship between performers and instruments. Related work involving PHYSMISM, of which the friction controller is an integral part, discusses how the physical interface might go beyond simply improving the level of intimacy that a performer has with their instrument by allowing for creative exploration through its use (Gelineck and Serafin 2010). This is interesting in two ways. Firstly, as PHYSMISM would allow physical models to be played in ways that their acoustic counterparts could not be played, it could lead to potential new sounds. Secondly, while the feel of and sensations involved in playing an instrument are crucial to a performer (Essl and O’Modhrain 2006), they can also impact the compositional or inventive aspect of musical creativity. In my own work, I have employed vibrotactile feedback not only to aid my performances through enhanced haptic sensation, but also to allow me to access how my music actually feels during the process of its creation (Hayes 2013). The act of composing becomes an embodied experience itself.

Turning back to performers, Young’s Hyperbow has been used by professional violinists, among others, in various performance settings (Young 2002b). However, in reviewing the literature related to this paper, what seems to be missing is the voice of the performers who have worked with these instruments. Summarising comments on observational studies have their place, but in-depth descriptions of practice and ethnographic inquiry into performances, rehearsals, and recordings made using these instruments can only help to legitimise the importance of this work. It is easy to imagine how performers and composers might benefit from being able to explore friction within a NIME and it would be helpful to read more about this too. As with most NIME research, we need more long-term accounts from those who regularly play, perform with, or workshop these often under-explored instruments.